1. Field of the Invention
This invention relates to galvanizing fluxes, their composition and their use. More particularly, this invention relates to flux compositions containing novel foaming compounds.
2. Prior Art
In hot-dip galvanizing a bath of molten zinc is covered with a flux usually referred to as a top-flux and articles to be galvanized are lowered into the molten zinc bath through the flux. The top flux layer cleans and prepares the article for the reception of a metal coating. It is known in galvanizing practice to add a small amount of an organic material to the top-flux such as ammonium chloride or zinc ammonium chloride to produce a frothy layer on the surface of the molten metal in the galvanizing pot. A flux which in use forms such a frothy layer is known as a foaming flux or a foaming top-flux. This froth or foam serves to trap vapors and gases and retard the rate of volatilization of the flux. Additionally, the foaming flux must be of sufficient depth to permit the flux to clean the article to be dipped before contacting the molten metal. The use of fluxes with foaming agents permits a continuous, adherent film of zinc which is substantially free of pin holes and other impurifications on the surface of the metallic article to be galvanized. Organic materials commonly used to cause foaming are bran, glycerol, tallow, sawdust and certain cellulose derivatives. These foaming agents suffer from the disadvantage that after a period of use they cause the viscosity of the flux to increase thereby retarding the rate of wetting of the article to be galvanized which leads to imperfect galvanizing, making it difficult for their metal objects to penetrate the flux and increasing the rate of which the flux is carried away with the finished article.